Method for Protecting a Gate Structure During Contact Formation

ABSTRACT

Various semiconductor devices are disclosed. An exemplary device includes: a substrate; a gate structure disposed over the substrate, wherein the gate structure includes a source region and a drain region; a first etch stop layer disposed over the gate structure, a second etch stop layer disposed over the source region and the drain region; a dielectric layer disposed over the substrate; and a gate contact, a source contact, and a drain contact. The dielectric layer is disposed over both etch stop layers. The gate contact extends through the dielectric layer and the first etch stop layer to the gate structure. The source contact and the drain contact extend through the dielectric layer and the second etch stop layer respectively to the source region and the drain region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/475,245, which was filed on May 18, 2012, which is a divisional ofU.S. application Ser. No. 12/428,011, filed Apr. 22, 2009, issued asU.S. Pat. No. 8,202,776, the entire disclosure of which is incorporatedherein by reference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. Conventional IC processinginvolves forming one or more contacts to various features of an IC. Forexample, oftentimes, contact openings are simultaneously formed to areasof a substrate (or wafer) (e.g., doped regions) and gate structuresdisposed thereover. It has been observed that the traditional processesfor forming contact openings to the substrate and gate structures mayresult in etching portions of the gate structure, such as the gate stack(e.g., a polysilicon and/or gate electrode). This over-etching of thegate structure can lead to undesirable contact resistance and degradedevice performance.

Accordingly, what is needed is a method for manufacturing an integratedcircuit device that addresses the above stated issues.

SUMMARY

A semiconductor device and method for manufacturing a semiconductordevice is disclosed. In one embodiment, the method includes providing asubstrate and forming at least one gate structure over the substrate andforming a plurality of doped regions in the substrate. The methodfurther comprises forming an etch stop layer over the substrate;removing a first portion of the etch stop layer, wherein a secondportion of the etch stop layer remains over the plurality of dopedregions; forming a hard mask layer over the substrate; and removing afirst portion of the hard mask layer, wherein a second portion of thehard mask layer remains over the at least one gate structure. The methodcan further comprise forming a first contact through the second portionof the hard mask layer to the at least one gate structure, and a secondcontact through the second portion of the etch stop layer to theplurality of doped regions.

In one embodiment, the method includes providing a substrate and formingat least one gate structure over the substrate, wherein the at least onegate structure comprises a dummy gate. The method further comprisesforming an etch stop layer over the substrate, including over the atleast one gate structure; forming a first interlevel dielectric (ILD)layer over the etch stop layer; and performing a chemical mechanicalpolishing (CMP) process on the first ILD and etch stop layer until a topportion of the at least one gate structure is exposed. The method canfurther comprise replacing the dummy gate of the at least one gatestructure; forming a hard mask layer over the top portion of the atleast one gate structure; forming a second ILD layer over the first ILDlayer, including over the hard mask layer; and forming one or morecontact openings to the at least one gate structure and to thesubstrate.

In one embodiment, the semiconductor device includes a substrate havingat least one gate structure disposed thereover and a plurality of dopedregions disposed therein; a hard mask layer disposed over the at leastone gate structure; an etch stop layer disposed over the plurality ofdoped regiona; a dielectric layer disposed over the hard mask layer andetch stop layer; and one or more contacts, wherein at least one contactextends through the dielectric layer and the hard mask layer to the atleast one gate structure, and wherein at least one contact extendsthrough the dielectric layer and the etch stop layer to the plurality ofdoped regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of a method for fabricating an integrated circuitdevice according to aspects of the present embodiments; and

FIGS. 2A-2N are various cross-sectional views of embodiments of anintegrated circuit device during various fabrication stages according tothe method of FIG. 1.

DETAILED DESCRIPTION

The present disclosure relates generally to methods for manufacturingintegrated circuit devices, and more particularly, to a method formanufacturing an integrated circuit device with improved deviceperformance.

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of theinvention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

With reference to FIGS. 1 through 2N, a method 100 and a semiconductordevice 200 are collectively described below. FIG. 1 is a flow chart ofone embodiment of the method 100 for making the semiconductor device200. FIGS. 2A-2N are various cross-sectional views of the semiconductordevice 200 according to one embodiment, in portion or entirety, duringvarious fabrication stages of the method 100. The semiconductor device200 may be an integrated circuit, or portion thereof, that may comprisestatic random access memory (SRAM), memory cells, and/or logic circuits;passive components such as resistors, capacitors, inductors, and/orfuses; active components, such as P-channel field effect transistors(PFETs), N-channel field effect transistors (NFETs),metal-oxide-semiconductor field effect transistors (MOSFETs),complementary metal-oxide-semiconductor transistors (CMOSs), bipolartransistors, high voltage transistors, and/or high frequencytransistors; other suitable components; and/or combinations thereof. Itis understood that additional steps can be provided before, during, andafter the method 100, and some of the steps described below can bereplaced or eliminated, for additional embodiments of the method 100. Itis further understood that additional features can be added in thesemiconductor device 200, and some of the features described below canbe replaced or eliminated, for additional embodiments of thesemiconductor device 200.

The semiconductor device 200 may be fabricated in a gate first process,gate last process, or hybrid process including a gate first process anda gate last process. In the gate first process, a metal gate structuremay be formed first and may be followed by a CMOS process flow tofabricate the final device. In the gate last process, a dummy poly gatestructure may be formed first and may be followed by a normal CMOSprocess flow until deposition of an interlayer dielectric (ILD), andthen the dummy poly gate structure may be removed and replaced with ametal gate structure. In the hybrid gate process, a metal gate structureof one type of device may be formed first and a metal gate structure ofanother type of device may be formed last.

Referring to FIGS. 1 and 2A, the method 100 begins at step 102 wherein asubstrate 210 including at least one isolation region 212 is provided.In the present embodiment, the substrate 210 is a semiconductorsubstrate. The semiconductor substrate 210 may comprise an elementarysemiconductor including silicon or germanium in crystal,polycrystalline, or an amorphous structure; a compound semiconductorincluding silicon carbide, gallium arsenic, gallium phosphide, indiumphosphide, indium arsenide, and/or indium antimonide; an alloysemiconductor including SiGe, GaAsP, AlinAs, AlGaAs, GaInAs, GaInP,and/or GaInAsP; any other suitable material; and/or combinationsthereof. In one embodiment, the alloy semiconductor substrate may have agradient SiGe feature in which the Si and Ge composition change from oneratio at one location to another ratio at another location of thegradient SiGe feature. In another embodiment, the alloy SiGe is formedover a silicon substrate. In another embodiment, a SiGe substrate isstrained. Furthermore, the semiconductor substrate may be asemiconductor on insulator, such as a silicon on insulator (SOI), or athin film transistor (TFT). In some examples, the semiconductorsubstrate may include a doped epi layer or a buried layer. In otherexamples, the compound semiconductor substrate may have a multilayerstructure, or the silicon substrate may include a multilayer compoundsemiconductor structure. In some embodiments, the substrate 210 maycomprise a non-semiconductor material, such as glass.

The substrate 210 may include various doping configurations depending ondesign requirements as known in the art. In some embodiments, thesubstrate 210 may include doped regions. The doped regions may be dopedwith p-type or n-type dopants. For example, the doped regions may bedoped with p-type dopants, such as boron or BF₂; n-type dopants, such asphosphorus or arsenic; and/or combinations thereof. The doped regionsmay be formed directly on the semiconductor substrate, in a P-wellstructure, in a N-well structure, in a dual-well structure, or using araised structure. The semiconductor substrate 210 may further includevarious active regions, such as regions configured for an N-typemetal-oxide-semiconductor transistor device (referred to as an NMOS) andregions configured for a P-type metal-oxide-semiconductor transistordevice (referred to as a PMOS). It is understood that the semiconductordevice 200 may be formed by complementary metal-oxide-semiconductor(CMOS) technology processing, and thus some processes are not describedin detail herein.

The at least one isolation region 212 may be formed on the substrate 210to isolate various regions, for example, to isolate NMOS and PMOStransistor device regions. The isolation region 212 may utilizeisolation technology, such as local oxidation of silicon (LOCOS) orshallow trench isolation (STI), to define and electrically isolate thevarious regions. In the present embodiment, the isolation region 212includes a STI. The isolation region 212 may comprise silicon oxide,silicon nitride, silicon oxynitride, fluoride-doped silicate glass(FSG), a low-K dielectric material, other suitable materials, and/orcombinations thereof. The isolation region 212, and in the presentembodiment, the STI, may be formed by any suitable process. As oneexample, the formation of an STI may include patterning thesemiconductor substrate by a conventional photolithography process,etching a trench in the substrate (for example, by using a dry etching,wet etching, and/or plasma etching process), and filling the trench (forexample, by using a chemical vapor deposition process) with a dielectricmaterial. In some embodiments, the filled trench may have a multi-layerstructure such as a thermal oxide liner layer filled with siliconnitride or silicon oxide.

Referring to FIGS. 1 and 2A-2B, at step 104, at least one gate structure220 is formed over the substrate 210. The gate structure 220 may beformed by any suitable process. For example, the gate structure 220 maybe formed by conventional deposition, photolithography patterning, andetching processes, and/or combinations thereof. The deposition processesmay include chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), high density plasma CVD (HDPCVD),metal organic CVD (MOCVD), remote plasma CVD (RPCVD), plasma enhancedCVD (PECVD), epitaxial growth methods (e.g., selective epitaxy growth),sputtering, plating, spin-on coating, other suitable methods, and/orcombinations thereof. The photolithography patterning processes mayinclude photoresist coating (e.g., spin-on coating), soft baking, maskaligning, exposure, post-exposure baking, developing the photoresist,rinsing, drying (e.g., hard baking), other suitable processes, and/orcombinations thereof. The photolithography exposing process may also beimplemented or replaced by other proper methods such as masklessphotolithography, electron-beam writing, ion-beam writing, and/ormolecular imprint. The etching processes may include dry etching, wetetching, and/or other etching methods (e.g., reactive ion etching). Theetching process may also be either purely chemical (plasma etching),purely physical (ion milling), and/or combinations thereof. It isunderstood that the at least one gate structure may be formed by anycombination of the processes described herein.

In the present embodiment, referring to FIG. 2A, a gate stack comprisinga high-k dielectric layer 222 and a dummy gate layer 224 is formed. Thehigh-k dielectric layer 222 is formed over the substrate 210. The high-kdielectric layer 222 may include hafnium oxide (HfO₂), hafnium siliconoxide (HfSiO), hafnium silicon oxynitride (HfSiON), hafnium tantalumoxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide(HfZrO), metal oxides, metal nitrides, metal silicates, transitionmetal-oxides, transition metal-nitrides, transition metal-silicates,oxynitrides of metals, metal aluminates, zirconium silicate, zirconiumaluminate, silicon oxide, silicon nitride, silicon oxynitride, zirconiumoxide, titanium oxide, aluminum oxide, hafnium dioxide-alumina(HfO₂—Al₂O₃) alloy, other suitable high-k dielectric materials, and/orcombinations thereof.

In the present embodiment, the dummy gate layer 224 comprisespolycrystalline silicon. The gate stack may be formed by any suitableprocess, including the processes described herein. In one example, thehigh-k dielectric layer 222 and dummy gate layer 224 are deposited overthe substrate 210. Then, a layer of photoresist is formed over the dummygate layer 224 by a suitable process, such as spin-on coating, andpatterned to form a patterned photoresist feature by a properlithography patterning method. Antireflective coating layers (e.g., atop antireflective coating layer and/or a bottom antireflective coatinglayer) may be formed adjacent the layer of photoresist. The pattern ofthe photoresist can then be transferred by a dry etching process to theunderlying layers (i.e., the high-k dielectric layer 222 and the dummygate layer 224) to form the gate stack as shown in FIG. 2A. Thephotoresist layer may be stripped thereafter. In another example, a hardmask layer is formed over the dummy gate layer 224; a patternedphotoresist layer is formed on the hard mask layer; the pattern of thephotoresist layer is transferred to the hard mask layer and thentransferred to the dummy gate layer 224 and the high-k dielectric layer222 to form the gate stack of the gate structure 220. It is understoodthat the above examples do not limit the processing steps that may beutilized to form the gate stack 220. It is further understood that thegate stack of the gate structure 220 may comprise additional layers. Forexample, the gate stack may additionally include an interfacial layer,such as silicon oxide, interposed between the substrate 210 and thehigh-k dielectric layer 222. In another embodiment, the gate stack maycomprise a capping layer interposed between the dummy gate layer 224 andthe high-k dielectric layer 222.

A sealing layer 225 is formed on the sidewalls of the gate stack of thegate structure 220. In the present embodiment, the sealing layer 225 isformed on the sidewalls of the high-k dielectric layer 222 and dummygate layer 224. The sealing layer 225 may include a dielectric material,such as silicon nitride, silicon oxide, silicon oxynitride, othersuitable material, and/or combinations thereof. The sealing layer 225may include a single layer or multiple layer configuration. It should benoted that the sealing layer 225 may protect the gate stack of the gatestructure 220 from damage or loss during subsequent processing, and mayalso prevent oxidation during subsequent processing. The sealing layer225 is formed by any suitable process to any suitable thickness,including the processes described herein.

Referring to FIG. 2B, lightly doped source/drain (LDD) regions 226 areformed. The LDD regions 226 may be formed in the substrate 210 by one ormore implantation processes, such as an ion implantation process. Thedoping species may depend on the type of device being fabricated, suchas an NMOS or PMOS device. For example, the LDD regions 226 may be dopedwith p-type dopants, such as boron or BF₂; n-type dopants, such asphosphorus or arsenic; and/or combinations thereof. The LDD regions 226may comprise various doping profiles. The LDD regions 226 may be alignedwith an outer edge of the sealing layer 225 following the ionimplantation process. As previously noted, the sealing layer 225 mayprovide protection to prevent contamination or damage to the gate stackcomprising the high-k dielectric layer 222 and dummy gate layer 224during subsequent processing. Thus, the integrity of the gate structure220 may be maintained which may result in better device performance andreliability. Additionally, it should be noted that during a subsequentannealing process (e.g., activation process) the dopants in the LDDregions 226 may diffuse towards the sidewalls of the gate stackcomprising the high-k dielectric layer 222 and dummy gate layer 224 suchthat a portion of each of the LDD regions 226 may extend underneath aportion of the sealing layer 225.

Following formation of the LDD regions 226, conventional spacer liner227, gate spacers 228, and S/D regions 230 are formed. The spacer liner227 and gate spacers 228 are formed by any suitable process to anysuitable thickness, including the processes described herein. In thepresent embodiment, the spacer liner 227 comprise an oxide material(e.g., silicon oxide), and the gate spacers 228, which are positioned oneach side of the gate structure 220, comprise a nitride material (e.g.,silicon nitride). The gate spacers 228 may comprise a dielectricmaterial such as silicon nitride, silicon oxide, silicon carbide,silicon oxynitride, other suitable materials, and/or combinationsthereof. The spacer liner 227 and/or gate spacers 228 may comprise amultilayer structure. The gate spacers 228 may be used to offset the S/Dregions 230 (also referred to as heavily doped source/drain regions).The S/D regions 230 may be formed in the substrate 210 by one or moreimplantation processes, such as an ion implantation process. The dopingspecies may depend on the type of device being fabricated, such as anNMOS or PMOS device. For example, the S/D regions 230 may doped withp-type dopants, such as boron or BF₂; n-type dopants, such as phosphorusor arsenic; and/or combinations thereof. The S/D regions 230 maycomprise various doping profiles, and the S/D regions 230 may be alignedwith an outer edge of the spacers 228 following the ion implantationprocess. The S/D regions 230 may further include raised S/D regions insome embodiments. Also, one or more contact features (e.g., silicideregions) may be formed on the S/D regions 230 by a salicidation (orself-aligned silicidation) process.

Referring to FIG. 2C, an etch stop layer (ESL) 232 and interlayer (orinter-level) dielectric (ILD) layer 234 may be formed over thesemiconductor device 200, including over the at least one gatestructure, by any suitable process, such as CVD. The ESL 232 may includesilicon nitride, silicon oxynitride, amorphous carbon material, siliconcarbide and/or other suitable materials. The ESL 232 composition may beselected based upon etching selectivity to one or more additionalfeatures of the semiconductor device 200. In the present embodiment, theESL 232 is a contact etch stop layer (CESL) comprising silicon nitride.ESL 232 further comprises any suitable thickness. In the presentembodiment, ESL 232 comprises a thickness of about 200 Å.

The ILD layer 234 comprises a dielectric material. The dielectricmaterial may comprise silicon oxide, silicon nitride, siliconoxynitride, spin-on glass (SOG), fluorinated silica glass (FSG), carbondoped silicon oxide (e.g., SiCOH), Black Diamond® (Applied Materials ofSanta Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon,Parylene, BCB (bis-benzocyclobutenes), Flare, SiLK (Dow Chemical,Midland, Mich.), polyimide, non-porous materials, porous materials,and/or combinations thereof. In some embodiments, the ILD layer 234 mayinclude a high density plasma (HDP) dielectric material (e.g., HDPoxide) and/or a high aspect ratio process (HARP) dielectric material(e.g., HARP oxide). The ILD layer 234 comprises any suitable thickness.In the present embodiment, ILD layer 234 comprises a thickness of about4500 Å. It is understood that the ILD layer 234 may comprise one or moredielectric materials and/or one or more dielectric layers.

Subsequently, the ESL 232 and/or ILD layer 234 are planarized by achemical mechanical polishing (CMP) process until a top portion of theat least one gate structure 220 overlying the semiconductor substrate210 is exposed as illustrated in FIG. 2D. The CMP process may have ahigh selectivity to provide a substantially planar surface for the gatestructure 220, ESL 232, and ILD layer 234. The CMP process may also havelow dishing and/or metal erosion effect.

Referring to FIG. 2E and FIG. 2F, a gate replacement process isperformed. The dummy gate layer 224 is removed and replaced by a metalgate. For example, in the present embodiment, the dummy gate layer 224is replaced by a work function layer 236 and a gate layer 238. The dummygate layer 224 is removed to form a trench (or recess) in the gatestructure 220 by any suitable process, including the processes describedherein. The work function layer 236 and gate layer 238 may then beformed in the trench (or recess) of the gate structure 220. The workfunction layer 236 is formed over the high-k dielectric layer 222. Thework function layer 236 is tuned to have a proper work function andcomprises any suitable material. For example, if a P-type work functionmetal (P-metal) for a PMOS device is desired, TiN, WN, or W may be used.On the other hand, if an N-type work function metal (N-metal) for NMOSdevices is desired, TiAl, TiAlN, or TaCN, may be used. In someembodiments, the work function layer 236 may include doped-conductingmetal oxide materials. The gate layer 238 comprises a conductivematerial, such as aluminum, copper, tungsten, titanium, tantulum,titanium nitride, tantalum nitride, nickel silicide, cobalt silicide,TaC, TaSiN, TaCN, TiAl, TiAlN, other suitable materials, and/orcombinations thereof. Further, the gate layer 238 may be dopedpolycrystalline silicon with the same or different doping. In thepresent embodiment, the gate layer 238 comprises aluminum. It isunderstood that additional layers may be formed above and/or below thework function layer 236 and/or gate layer 238, including liner layers,interface layers, seed layers, adhesion layers, barrier layers, etc. Itis further understood that the work function layer 236 and gate layer238 may comprise one or more materials and/or one or more layers. Thework function layer 236 and gate layer 238 may be formed by any suitableprocess to any suitable thickness, including the processes describedherein.

Subsequent to the formation of the work function layer 236 and gatelayer 238, a CMP process may be performed to provide a substantiallycoplanar surface of the gate layer 238 (e.g., aluminum gate layer) ofthe gate structure 220. Conventional processing would continue to forman ILD layer over the semiconductor device 200, including over the gatestructure; etch one or more contact openings to the S/D regions and/orthe gate structure; and then, fill the one or more contact openings witha conductive material. It has been observed that formation of the one ormore contact openings may undesirably etch portions of the gate stack(e.g., the gate layer). This can result since it takes longer to etch tothe S/D regions than the gate stack. Thus, because the gate stack lacksprotection, a top portion of the gate stack is exposed prior to a topportion of the S/D regions, which leads to portions of the gate stackbeing etched away. Such etching-through of the gate stack can lead tohigher than desirable contact resistance, which may negatively affectoverall device performance. Accordingly, in the present embodiment, aprotective layer is formed over the gate structure. The protective layermay prevent the etching-through issue arising from the continued etchingutilized to form contact openings to the S/D regions.

Referring to FIGS. 1 and 2G, at step 106, a hard mask (or protective)layer 240 is formed over the semiconductor device 200. Morespecifically, the hard mask layer 240 is formed over the ILD layer 234,including over the gate structure 220. In the present embodiment, thehard mask layer 240 comprises silicon nitride. The hard mask layer 240may include a silicon oxynitride, amorphous carbon material, siliconcarbide, other suitable nitrogen-containing materials, other suitabledielectric materials, and/or combinations thereof. The hard mask layer240 may be formed by any suitable process, such as CVD. The hard masklayer 240 may include a single layer or multiple layers. Further, thehard mask layer 240 comprises any suitable thickness. In someembodiments, the hard mask layer 240 and the ESL 232 comprisesubstantially a same thickness. For example, in the present embodiment,the hard mask layer 240 comprises a thickness of about 200 Å.

At step 108, one or more portions of the hard mask layer are removed,wherein a portion of the hard mask layer remains over the at least onegate structure. The one or more portions of the hard mask layer 240 areremoved by any suitable process, including the processes describedherein. In the present embodiment, a photoresist layer 242 is formedover the hard mask layer 240 to any suitable thickness. Then, thephotoresist layer 242 is patterned by a conventional photolithographyprocess and/or processes to create one or more first portions 242A andone or more second portions 242B as shown in FIG. 2H. Thephotolithography patterning processes may include photoresist coating(e.g., spin-on coating), soft baking, mask aligning, exposure,post-exposure baking, developing the photoresist, rinsing, drying (e.g.,hard baking), other suitable processes, and/or combinations thereof. Thephotolithography exposing process may also be implemented or replaced byother proper methods such as maskless photolithography, electron-beamwriting, ion-beam writing, and/or molecular imprint. Further, in someembodiments, the photolithography patterning and exposing process mayimplement krypton fluoride (KrF) excimer lasers, argon fluoride (ArF)excimer lasers, immersion lithography, extreme ultra-violet (EUV)radiation, and/or combinations thereof. It is understood that additionallayers may be formed above or below the photoresist layer 242, such asone or more antireflective coating layers.

The patterned photoresist layer 242 comprising first and second portions242A, 242B define unprotected and protected portions of the hard masklayer 240. The first portions 242A define unprotected portions of thehard mask layer 240. The second portions 242B define protected portionsof the hard mask layer 240. The second portions 242B pattern and defineportions of the hard mask layer 240 that will remain over the at leastone gate structure 220. Referring to FIG. 2I, the first portions 242A ofthe photoresist layer 242 and the unprotected portions of the hard masklayer 240, which underlie the first portions 242A, are removed. Thefirst portions 242A and unprotected portions of the hard mask layer 240are removed by any suitable process. It is understood that the firstportions 242A and unprotected portions of the hard mask layer 240 may besimultaneously or independently removed. For example, removing suchportions may include an etching process. The etching process may includemultiple etching steps and etching solutions to remove the firstportions 242A and/or unprotected portions of the hard mask layer 240.The etching process may comprise one or more dry etching processes, wetetching processes, other suitable etching methods (e.g., reactive ionetching), and/or combinations thereof.

Subsequently, the photoresist layer 242 (i.e., second portions 242B) maybe removed by any suitable process, such as a photoresist strippingprocess. Referring to FIG. 2J, the protected portions of the hard masklayer 240, which were underlying second portions 242B, remain over thesubstrate 210. In the present embodiment, the hard mask layer 240remains extending over the entirety of the gate structure 220. It isunderstood that the remaining hard mask layer 240 may extend anysuitable distance (for example, the hard mask layer 240 may extend overonly the gate stack of the gate structure 220). It is further understoodthat the process utilized to pattern the hard mask layer 240 is notlimited to the example described herein. For example, in someembodiments, a photoresist layer 242 may not be deposited over the hardmask layer 240, and the hard mask layer 240 may be patterned by aconventional lithography process, such as utilizing a mask (e.g., a maskutilized to pattern the gate stack).

Referring to FIGS. 1 and 2K, at step 110, an ILD layer 244 is formedover the semiconductor device 200. In the present embodiment, the ILDlayer 244 is formed over the hard mask layer 240. The ILD layer 244comprises a dielectric material, such as silicon oxide, silicon nitride,silicon oxynitride, SOG, FSG, carbon doped silicon oxide (e.g., SiCOH),Black Diamond® (Applied Materials of Santa Clara, Calif.), Xerogel,Aerogel, amorphous fluorinated carbon, Parylene, BCB, Flare, SiLK (DowChemical, Midland, Mich.), polyimide, non-porous materials, porousmaterials, other suitable dielectric materials, and/or combinationsthereof. In some embodiments, the ILD layer 244 may include a HDP oxideand/or a HARP oxide. The ILD layer 244 comprises any suitable thickness.The ILD layer 244 may comprise one or more dielectric materials and/orone or more dielectric layers. Subsequently, the ILD layer 244 may beplanarized by a CMP process.

Referring to FIG. 1 and FIGS. 2L-2N, at step 112, one or more contactsare formed to the substrate and/or at least one gate structure. In thepresent embodiment, one or more contacts are formed to the S/D regions230 and the gate structure 220. Forming the one or more contactscomprises performing a first etching process and a second etchingprocess. The first etching process is performed on the semiconductordevice 200 to remove a portion of the ILD layers 234, 244. In thepresent embodiment, the first etching process is performed on the ILDlayers 234, 244 until the ESL layer 232 over the S/D regions 230 and thehard mask layer 240 over the gate structure 220 is reached and/orexposed as illustrated in FIG. 2L. The removed portions of ILD layers234, 244 form first contact openings and/or trenches 246A, 248A to theS/D regions 230 and gate structure 220. The first (or main) etchingprocess has an etching selectivity between the ESL 232/hard mask layer240 and the ILD layers 234, 244. Accordingly, the first etching processmay stop at the ESL 232/hard mask layer 240. For example, with the ESL232/hard mask layer 240 comprising silicon nitride and the ILD layers234, 244 comprising oxide, the first etching process may exhibit a highetching selectivity between silicon nitride and oxide, such that thefirst etching process removes ILD layers 234, 244 without substantiallyaffecting the ESL 232/hard mask layer 240.

As is evident from FIG. 2L and as noted above, in conventionalprocessing, a top portion of the gate structure 220 will be reachedbefore a top portion of the S/D regions 230 when forming contactopenings. This often results in the undesirable etching of the gatestructure 220. In the present embodiment, the hard mask layer 240 canprotect the gate structure 220, particularly the gate layer 238 of thegate structure 220, while the first etching process forms contactopenings to the ESL 232. The hard mask layer 240 may function as an etchstop layer for the first etching process. Thus, etching portions of thegate structure 220, such as the gate layer 238, is prevented. Suchprevention may provide improved device performance by reducing thecontact resistance arising at the gate structure.

The second etching process is performed on the semiconductor device 200to remove a portion of the ESL 232 and hard mask layer 240. The secondetching process is performed on the ESL layer 232 and hard mask layer240 until a top portion of the S/D regions 230 and a top portion of thegate structure 220 (e.g., gate layer 238) is reached and/or exposed asillustrated in FIG. 2M. The removed portions of ILD layers 234, 244 andESL 232/hard mask layer 240 form second contact openings and/or trenches246B, 248B to the S/D regions 230 and gate structure 220. The secondetching process has an etching selectivity between the ESL 232/hard masklayer 240 and the ILD layers 234, 244. For example, with the ESL232/hard mask layer 240 comprising silicon nitride and the ILD layers234, 244 comprising oxide, the second etching process may exhibit a highetching selectivity between silicon nitride and oxide, such that thesecond etching process removes ESL 232/hard mask layer 240 withoutsubstantially affecting the ILD layers 234, 244. In the presentembodiment, the second etching process comprises a silicon nitrideetching process.

The first and second etching processes may comprise one or more dryetching processes, wet etching processes, other suitable processes(e.g., reactive ion etching), and/or combinations thereof. The etchingprocesses may be either purely chemical (plasma etching), purelyphysical (ion milling), and/or combinations thereof. For example, a dryetching process may be implemented in an etching chamber using processparameters including a radio frequency (RF) source power, a bias power,a pressure, a flow rate, a wafer temperature, other suitable processparameters, and/or combinations thereof. The dry etching process mayimplement an oxygen-containing gas, fluorine-containing gas (e.g., CF₄,SF₆, CH₂F₂, CHF₃, and/or C₂F₆), chlorine-containing gas (e.g., Cl₂,CHCl₃, CCl₄, and/or BCl₃), bromine-containing gas (e.g., HBr and/orCHBR₃), iodine-containing gas, other suitable gases and/or plasmas,and/or combinations thereof. In some embodiments, the dry etchingprocess utilizes an O₂ plasma treatment and/or an O₂/N₂ plasmatreatment. Further, the dry etching process may be performed for anysuitable time. A wet etching process may utilize a hydrofluoric acid(HF) solution for a HF dipping process. The HF solution may have anysuitable concentration (e.g., 1:100). In some embodiments, a wet etchingprocess may apply a diluted hydrofluoric acid to the semiconductordevice 200. It is understood that the first and second etching processesmay include multiple etching steps and etching solutions.

Referring to FIG. 2N, subsequently, contacts 250, 252 may be formed byany suitable process, including the processes described herein. Contacts250 provide contact to the S/D regions 230 (via silicide regions), andcontact 252 provides contact to the gate structure 220 (for example,coupled to a gate electrode of the gate structure 220). The contacts250, 252 may be formed by filling second contact openings 246B, 248Bwith a conductive material. The conductive material may comprisealuminum, copper, tungsten, titanium, tantulum, titanium nitride,tantalum nitride, nickel silicide, cobalt silicide, TaC, TaSiN, TaCN,TiAl, TiAlN, other suitable materials, and/or combinations thereof. Itis understood that the semiconductor device 200 may undergo further CMOSor MOS technology processing to form various features known in the art.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device comprising: a substrate; agate structure disposed over the substrate, wherein the gate structureincludes a source region and a drain region disposed in the substrate,and wherein the gate structure interposes the source region and thedrain region; a first etch stop layer disposed over the gate structure;a second etch stop layer disposed over the source region and the drainregion; a dielectric layer disposed over substrate, wherein thedielectric layer is disposed over the first etch stop layer and thesecond etch stop layer; and a gate contact, a source contact, and adrain contact, wherein the gate contact extends through the dielectriclayer and the first etch stop layer to the gate structure, and thesource contact and the drain contact extend through the dielectric layerand the second etch stop layer respectively to the source region and thedrain region.
 2. The semiconductor device of claim 1, wherein the gatestructure includes a high-k gate dielectric and a metal gate electrode,the gate contact being coupled to the metal gate electrode.
 3. Thesemiconductor device of claim 1, wherein the first etch stop layer andthe second etch stop layer are a substantially same type of material. 4.The semiconductor device of claim 3, wherein the substantially same typeof material is silicon nitride.
 5. The semiconductor device of claim 1,wherein the first etch stop layer and the second etch stop layer have asubstantially same thickness.
 6. The semiconductor device of claim 1,wherein the source contact and the drain contact extend through a seconddielectric layer to the source region and the drain region.
 7. Thesemiconductor device of claim 6, wherein the second dielectric layer isdisposed between the second etch stop layer and the dielectric layerdisposed over the first and second etch stop layers.
 8. A semiconductordevice comprising: a substrate having at least one gate structuredisposed thereover and at least one doped region disposed therein; ahard mask layer disposed over the at least one gate structure; an etchstop layer disposed over the at least one doped region; a dielectriclayer disposed over the hard mask layer and etch stop layer; and one ormore contacts, wherein at least one contact extends through thedielectric layer and the hard mask layer to the at least one gatestructure, and wherein at least one contact extends through thedielectric layer and the etch stop layer to the at least one dopedregion.
 9. The semiconductor device of claim 8, wherein the at least onegate structure comprises a high-k gate dielectric and a metal gateelectrode.
 10. The semiconductor device of claim 9, wherein the at leastone contact extending through the dielectric layer and the hard masklayer is coupled to the metal gate electrode.
 11. The semiconductordevice of claim 8, wherein the hard mask layer and the etch stop layercomprise substantially a same type of material.
 12. The semiconductordevice of claim 11, wherein the substantially same type of material issilicon nitride.
 13. The semiconductor device of claim 8, wherein thehard mask layer and the etch stop layer comprise substantially a samethickness.
 14. The semiconductor device of claim 8, wherein the at leastone contact that extends through the dielectric layer and the etch stoplayer to the at least one doped region extends through a seconddielectric layer.
 15. The semiconductor device of claim 14, wherein thesecond dielectric layer is disposed between the second etch stop layerand the dielectric layer disposed over the first and second etch stoplayers.
 16. A semiconductor device comprising: a substrate having asource region and a drain region; a gate structure disposed over thesubstrate; a first silicon nitride layer disposed over the gatestructure; a second silicon nitride layer disposed over the sourceregion and the drain region; a first dielectric layer disposed over thefirst and second silicon nitride layers; a second dielectric layerdisposed between the first dielectric layer and the second siliconnitride layer; one or more contacts, wherein at least one contactextends through the dielectric layer and the first silicon nitride layerto the at least one gate structure, and wherein at least one contactextends through the first and second dielectric layers and the secondsilicon nitride layer to the source region and drain region.
 17. Thesemiconductor device of claim 16, wherein the gate structure comprises ahigh-k gate dielectric and a metal gate electrode.
 18. The semiconductordevice of claim 16, wherein the first and second silicon nitride layerscomprise substantially a same thickness.
 19. The semiconductor device ofclaim 16, wherein the first and second dielectric layers comprise anoxide material.
 20. The semiconductor device of claim 19, wherein theoxide material comprises silicon oxide, carbon doped silicon oxide,high-density plasma (HDP) oxide, high-aspect-ratio process (HARP) oxide,or combinations thereof.